When a strange murder takes place in the sleepy market town of Bakerbury. The local police are baffled by a crossword puzzle left on the body.

With their case going nowhere, they turn reluctantly to Cora Felton, a recent arrival in Bakerbury; whose fame as the eponymous Puzzle Lady suggests she can help DCI Hooper and the Bakerbury police solve its first murder case. But the eccentric Cora isn't who she claims to be, and as she throws herself into a murder case that has the town's residents baffled, she starts to gather allies and enemies in equal measure.